1. Field of the Invention
The present invention relates to a straddle-type four wheeled vehicle provided with a gear transmission capable of changing a gear arrangement among several forward states and a backward state by operating a change pedal, and a reverse lock device for preventing the change to the backward state.
2. Description of the Related Art
In general, a straddle-type four wheeled vehicle of this type is configured such that a gear transmission is shifted up by pushing up a change pedal by a foot of a rider, conversely, the gear transmission is shifted down by pushing down the change pedal by the foot. A neutral state of the gear transmission is set between a forward first speed state and a forward second speed state in a shifting operation, therefore the gear transmission is shifted to the backward state by further pushing down the change pedal from the forward first speed state. In order to prevent any erroneous operation to the backward state, there is provided a reverse lock device for preventing the gear transmission from shifting from the forward first speed state to the backward state. In the case, the gear transmission can be shifted to the backward state by unlocking the reverse lock device.
FIG. 8 shows one example of a conventional reverse lock device in a straddle-type four wheeled vehicle. A change drum 201 is accommodated in a transmission case 200 integrally formed at a rear portion of a crankcase (not shown) of an engine. A lever chamber 203 for reverse lock is defined by using the outside of a generator cover fixed onto a side wall of the transmission case 200. The reverse lock device is constituted of an outer lever 205 arranged in the lever chamber 203; an annular stopper 210 fitted around an axial end 201a of the change drum 201; an inner lever 212 capable of locking and unlocking a locking portion 211 formed on the stopper 210; a rotating shaft 214 having the inner lever 212 and the outer lever 205 securely fixed thereto; and a transmission cable 215 connected to the tip of the outer lever 205. The inner lever 212 is urged by a return spring 216 in the direction indicated by an arrow L1, to thus abut against the outer peripheral surface of the stopper 210.
The change drum 201 shown in FIG. 8 is located at the forward first speed position corresponding to the forward first speed state of the gear transmission. When the change drum 201 is rotated by a predetermined angle from the above-described position (forward first speed position) in the direction indicated by an arrow D, the change drum 201 is moved to the backward position corresponding to the backward state of the gear transmission. Here, the locking of the tip of the inner lever 212 to the locking portion 211 at the forward first speed position can prevent the change drum 201 from rotating in the direction indicated by the arrow D, that is, can prevent any shift to the backward state (the backward state).
When the gear transmission is shifted to the backward state, the outer lever 205 is rotated in the direction indicated by an arrow L2 via the transmission cable 215 by operating an unlocking operating unit (not shown) such as an unlocking lever. As a consequence, the rotating shaft 214 and the inner lever 212 are rotated in the direction indicated by the arrow L2, so that the tip of the inner lever 212 is unlocked from the locking portion 211, thus unlocking the reverse lock.
Besides the above-described conventional example, Japanese Patent Application Laid-open No. 2004-161133 discloses a straddle-type four wheeled vehicle provided with a V belt-type continuously variable transmission, in which a change operating unit for changing a gear arrangement of a gear transmission is disposed in the vicinity of a grip of a handle bar and includes a reverse lock device.
The reverse lock device shown in FIG. 8 includes the lever chamber 203 defined by the generator cover fixed onto the side wall of the transmission case 200, the two levers 205 and 212, and the rotating shaft 214, both of the levers 205 and 212 being rotated around the axis of the rotating shaft 214 within a predetermined range of a turn track. Therefore, a large space for disposing the reverse lock device is needed sideways of the transmission case 200, and further, the number of component parts becomes greater. In other words, not only the size but also the weight of the engine is increased, with an attendant disadvantage of the increased cost of component parts.